Abstract
Ionic liquids (ILs) on the basis of metal containing anions and/or cations are of interest for a variety of technical applications e.g., synthesis of particles, magnetic or thermochromic materials. We present the synthesis and the results of electron paramagnetic resonance (EPR) spectroscopic analyses of a series of some new potential ionic liquids based on tetrachloridocuprates(II), [CuCl4]2−, with different sterically demanding cations: hexadecyltrimethylammonium 1, tetradecyltrimethylammonium 2, tetrabutylammonium 3 and benzyltriethylammonium 4. The cations in the new compounds were used to achieve a reasonable separation of the paramagnetic Cu(II) ions for EPR spectroscopy. The EPR hyperfine structure was not resolved. This is due to the exchange broadening, resulting from still incomplete separation of the paramagnetic Cu(II) centers. Nevertheless, the principal values of the electron Zeemann tensor (g║ and g┴) of the complexes could be determined. Even though the solid substances show slightly different colors, the UV/Vis spectra are nearly identical, indicating structural changes of the tetrachloridocuprate moieties between solid state and solution. The complexes have a promising potential e.g., as high temperature ionic liquids, as precursors for the formation of copper chloride particles or as catalytic paramagnetic ionic liquids.
Highlights
Ionic liquids (ILs) or ionic liquid crystals (ILCs) on the basis of metal containing anions and/or cations are of interest for a variety of technical applications e.g., as precursors for synthesis ofparticles, magnetic or thermochromic materials [1,2,3] or for usage as extraction agents [4] or catalysts [5,6,7,8]
Alkylpyridinium tetrahalidocuprate ILs and ILCs have been used as precursors for inorganic materials [2,14,15]
We present the syntheses and the results of electron paramagnetic resonance (EPR) spectroscopic analyses including temperature dependent measurements of some new tetrachloridocuprate(II)
Summary
Ionic liquids (ILs) or ionic liquid crystals (ILCs) on the basis of metal containing anions and/or cations are of interest for a variety of technical applications e.g., as precursors for synthesis of (nano)particles, magnetic or thermochromic materials [1,2,3] or for usage as extraction agents [4] or catalysts [5,6,7,8]. Metal containing ionic liquids provide the interesting feature of being electrochromic and/or magnetic [17,18] With their already known properties such as tunable acidity, polarity, amphiphilic character, coordinating ability, and miscibility with various compounds and properties due to the metal ion, these ILs could be the best candidates as catalysts for many chemical reactions as well as alternative solvents and morphology templates for inorganic materials at the same time. Reports on tetrahalidometalate-based ILs/ILCs and their applications as well as their characterization are relatively rare [2,10,11,12,13,19,20,21,22,23,24,25,26,27,28,29,30,31,32] This is somewhat surprising because metal containing ILs and ILCs may open the door towards a new valuable branch of IL research, due to its additional properties such as color, geometry, and magnetism, proffered by the metal ion composition. They were used to achieve a reasonable separation of the paramagnetic Cu(II) ions for EPR spectroscopy
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